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Smoking Raises Breast Cancer Risk for Women, Except Obese

A new study says smoking raises the risk of breast cancer for healthy-weight and overweight women, but not for women who are obese.

The report was presented over the weekend at a meeting of the American Association for Cancer Research in Florida. Researchers used data from the decades-long study called the Women’s Health Initiative, in which more than 3,000 of 76,000 women had breast cancer.

They looked at the body mass index of the women. The Associated Press writes:

Those who were healthy-weight or merely overweight, with BMIs under 30, were more likely to develop breast cancer if they smoked; the risk was 16 percent higher for those smoking for 10 to 29 years and 25 percent higher for those who smoked 30 to 49 years.

However, researchers saw no added breast cancer risk in obese smokers (BMI of 30 or above) compared to nonsmokers who weighed that much.

"That needs to be interpreted cautiously because it’s the first time that anyone’s examined whether the relationship of smoking with breast cancer is different by level of obesity," said Susan Gapstur, vice president of epidemiology at the American Cancer Society.

Researchers really have no explanation for the results. Many breast cancers are fueled by estrogen, and fat tissue makes that hormone. So it could be that obesity is contributing so much risk already that a smaller risk from smoking is less apparent.

"We cannot separate the effect of smoking from the effect of obesity," said lead researcher Juhua Luo, a West Virginia University scientist.

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